JP6975419B2 - Separator, coal ash manufacturing method, and coal ash cleaning system - Google Patents

Description

The present invention relates to a separation device for coal ash and unburned carbon, a method for producing coal ash, and a coal ash cleaning system.

Coal ash is an industrial waste generated in coal-fired power plants by nearly 10 million tons every year, and it is a great national loss to dispose of such coal ash. ing.

On the other hand, in the production of concrete, a method of mixing fine particle material with ready-mixed concrete has been used in order to increase its strength. Conventionally, river sand has been used as a fine aggregate for ready-mixed concrete, but since the amount of river sand that can be collected has decreased in recent years, sea sand has been used as a fine aggregate for ready-mixed concrete. However, collecting large amounts of sea sand not only spoils the coastal landscape, but also has a serious adverse effect on the ecosystem of the surrounding sea area. Therefore, in recent years, a fine particle material that can be used as a fine aggregate of ready-mixed concrete has been desired instead of river sand and sea sand.

From the above background, coal ash is considered as a fine particle material useful for fine aggregate of ready-mixed concrete. If a large amount of coal ash generated every year can be used for the fine aggregate of ready-mixed concrete, the strength of the concrete can be increased without wasting a large amount of river sand and sea sand, and a large amount of coal generated at a coal-fired power plant can be used. The ash can be effectively reused.

However, unburned carbon remains in the coal ash produced from coal burned as fuel in a coal-fired power plant, and this unburned carbon causes the coal ash to be a fine aggregate of ready-mixed concrete. There was a problem that it became difficult to use as.

When observing the surface of coal ash with a micrograph, etc., there are many solid unburned carbons that enclose minute spherical glassy or crystalline material composed of silicon or aluminum, and on the surface of the unburned carbons, there are many. It was found that fine irregularities and pores were formed. Therefore, when coal ash is mixed with ready-mixed concrete, unburned carbon adsorbs the admixture and hinders the action of the admixture, which makes it difficult to control the fluidity and air content of fresh concrete. .. Further, since it is necessary to increase the blending amount of the admixture in order to obtain a predetermined fluidity and air amount, there is also a problem that the manufacturing cost of concrete increases.

Therefore, there is a need for a method for producing coal ash with a reduced residual amount of unburned carbon. As such a method, coal ash is washed to reduce unburned carbon by a flotation method (see, for example, Patent Documents 1 and 2).

In Patent Document 1, the liquid to be treated is taken out from the circulation liquid outlet at the upper part of the treatment tank body, returned from the circulation liquid inlet at the lower part of the treatment tank body, and bubbles are injected into the lower part of the treatment tank body to inject the liquid to be treated. Is flowed along the inner peripheral surface of the main body of the treatment tank to generate a vortex in the liquid to be treated in the main body of the treatment tank, and bubbles are dispersed in the liquid to be treated and adhered to impurities to remove the impurities adhering to the bubbles. The method of floating is described.

Further, in Patent Document 2, in order to further reduce the amount of unburned carbon after washing, a step of kneading coal ash containing unburned carbon and an aqueous solution containing kerosene is added, and ultrasonic waves are further applied. Describes a method for reducing the amount of unburned carbon contained in the washed coal ash to 1% by mass or less.

Japanese Unexamined Patent Publication No. 2011-20070 Japanese Unexamined Patent Publication No. 2010-23018

However, in the method described in Patent Document 1, the amount of unburned carbon remaining in the coal ash after washing is about 1% by mass or more, and the amount of unburned carbon is 1% by mass or less to produce coal ash. It was difficult.

Further, in the separation device described in Patent Document 1, if the flow rate of the circulating fluid is small, it becomes difficult for a swirling flow to occur, and coal ash accumulates on the bottom of the separation tank, making it difficult to reduce the residual amount of unburned carbon. There was a problem. On the other hand, if the flow rate of the circulating liquid supplied from the circulating liquid outlet is increased so as not to deposit coal ash, the separated and floating unburned carbon is sucked from the circulating liquid inlet and stirred, and the unburned carbon becomes fine. There was a problem that the coal ash was converted, the circulation pump deteriorated, and large particles of coal ash also floated to the upper part of the separation tank and were removed together with the unburned carbon.

Further, the method described in Patent Document 2 has a problem that the scale of the apparatus is increased to about twice that of the method described in Patent Document 1. Further, in the method described in Patent Document 2, since it is necessary to attach a large-sized ultrasonic vibration element to the kneading device, there is a problem that the equipment becomes complicated.

In addition, in the device described in Patent Document 2, the installation location and the operation of the ultrasonic oscillator do not matter in a small laboratory scale, but when scaled up to an industrial scale, the installation location and ultrasonic waves The availability becomes a problem. Further, there is also a problem that the price of the device, the maintenance cost, and the running cost are about twice as high as those in the case of using the device described in Patent Document 1.

That is, in the prior art, unburned carbon of coal ash could be removed by using complicated equipment or using a high-cost cleaning method, but coal ash with simple equipment and low cleaning cost. There was a problem that unburned carbon could not be reduced.

The present invention solves the above problems. That is, the present invention realizes energy saving by increasing the removal rate of unburned carbon without miniaturizing the unburned carbon, suppressing deterioration of the pump that supplies water, and removing unburned carbon in a short time. It is an object of the present invention to provide a separation device capable of providing a capable separation device. It is also an object of the present invention to provide a method for producing coal ash and a cleaning system capable of reducing unburned carbon in coal ash with simpler equipment and lower cleaning cost than before.

The above problem can be solved by the following means [1] to [10].

[1] A separation tank that separates coal ash containing unburned carbon into unburned carbon and coal ash.
A water supply means for supplying new water into the separation tank from the water supply port provided at the bottom of the separation tank,
It is equipped with a bubble supply means that supplies bubbles into the separation tank from the bottom of the separation tank.
A separation device in which the separation tank is configured so that coal ash can be supplied from a position higher than the height of the water supply port.

[2] The lower part of the separation tank constitutes a side portion that is narrowed downward.
A water supply port is provided on the above side,
The separation device according to [1], wherein the vicinity of the water supply port of the water supply means is provided in a direction in which water can be supplied along the inner wall of the side portion.

[3] The separation device according to [1] or [2], wherein the bubble supply means is configured to supply bubbles from a water supply port.

[4] A coal ash supply means capable of supplying coal ash from a position higher than the height of the water supply port is provided.
The coal ash supply means supplies coal ash as a coal ash slurry containing coal ash and water, and finally to the total volume X (L) of the coal ash slurry and water to be charged into the separation tank. On the other hand, any of [1] to [3], which comprises means for adjusting the flow rate of the coal ash slurry supplied by the coal ash supply means to X × 9/100 to X × 55/100 (L / min). Separation device described in coal.

[5] A water supply process for supplying new water into the separation tank from a water supply port provided at the bottom of the separation tank, and
The bubble supply process that supplies bubbles into the separation tank from the bottom of the separation tank,
It has a coal ash supply process in which coal ash is supplied into the separation tank from a position higher than the height of the water supply port in a state where a predetermined amount of water and air bubbles are supplied into the separation tank.
In the separation tank, the unburned carbon contained in the coal ash is separated into the coal ash and the unburned carbon by the contact between the bubbles and the unburned carbon, and the residual amount of the unburned carbon is reduced to produce the coal ash. How to make coal ash.

[6] It has a step (A) of stirring a mixture containing coal ash containing unburned carbon, water, and oil 0.15 to 10% by mass and having a solid content concentration of 65 to 90% by mass. ,
It has a step (B1) of further adding water to the mixture obtained in the step (A) to form a coal ash slurry.
The coal ash slurry obtained in the step (B1) is put into a separation tank to which water and air bubbles are supplied to form a layer containing water and coal ash and a light layer containing unburned carbon adsorbed with oil. The method for producing coal ash according to [5], which comprises the step (B2) of separating into.

[7] The method for producing coal ash according to [6], wherein the mixture contains 5 to 30% by mass of water.

[8] The method for producing coal ash according to [6] or [7], wherein the mixture contains 0.2 to 10% by mass of oil.

[9] The coal ash according to any one of [6] to [8], which comprises an emulsification step of pre-stirring and emulsifying the water and oil used in the mixture before mixing with the coal ash containing unburned carbon. Manufacturing method.

[10] A coal ash agitator that agitates a mixture containing unburned carbon-containing coal ash, water and oil, and having a solid content concentration of 65 to 90% by mass.
A slurry container for further adding water to the stirred mixture to form a coal ash slurry,
The coal ash slurry is put into a separation tank to which water and air bubbles are supplied, and has a separation device for separating a layer containing water and coal ash and a light layer containing unburned carbon adsorbed with oil. , Coal ash cleaning system.

According to the separation device of the present invention, the removal rate of unburned carbon is increased without miniaturizing the unburned carbon, the deterioration of the pump for supplying water is suppressed, and the unburned carbon is removed in a short time to save energy. Can be realized. Further, according to the method for producing coal ash or the cleaning system of the present invention, unburned carbon of coal ash can be reduced with simpler equipment and lower cleaning cost than before.

It is a conceptual diagram of the separation apparatus which concerns on embodiment of this invention. It is a figure which looked at the separation apparatus which concerns on embodiment of this invention from the upper surface. It is a conceptual diagram of the coal ash washing system which concerns on embodiment of this invention. It is a conceptual diagram of the separation device to be compared.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.

The process of the method for producing coal ash (including fly ash) in which the residual amount of unburned carbon according to the present embodiment is reduced can be roughly divided into a step (A) and a step (B). The step (A) is a step of impregnating coal ash containing unburned carbon with water and oil to appropriately adjust the concentration of solid content, and then stirring the obtained mixture. The step (B) is a step of adding water to the mixture to prepare the content, and separating the mixture into a layer containing water and coal ash and a light layer containing unburned carbon adsorbed with oil.

By dividing the coal ash cleaning step into a step of stirring the coal ash and oil (kerosene, edible oil, etc.) (A) and a step of separating the coal ash and unburned carbon (B), each step The stirring function and the separation function are exhibited with high efficiency. Therefore, the efficiency of removing unburned carbon is greatly improved, and it becomes possible to produce coal ash with higher purity in a large amount and with high accuracy.

Even if the coal ash cleaning process is divided into two, the construction cost of the cleaning equipment does not increase, but rather it can contribute to the reduction of the construction cost of the cleaning equipment. This is because it is a cleaning process that can be realized without the need for a large flotation device as in the past. That is, the method using the process (A) and the process (B) facilitates simplification of the cleaning equipment and reduction of the cleaning cost.

Further, the step (B) can be divided into a step (B1) and a step (B2). The step (B1) is a step of further adding water to the mixture obtained in the step (A) to form a coal ash slurry. In the step (B2), the coal ash slurry obtained in the step (B1) is put into a separation tank to which water and bubbles are supplied, and an unburned layer containing water and coal ash and oil are adsorbed. This is a process of separating into a light layer containing carbon. By performing the step (B1) before the step (B2), the coal ash is easily dispersed in the separation tank.

The separation device of the present invention can be used in the step (B2).

(Configuration of separator)
The separation device 1 shown in FIG. 1 includes a separation tank 2, a water supply means 3, a microbubble generator 4, a coal ash supply means 5, and the like. Further, FIG. 2 is a view of the separation device of FIG. 1 as viewed from above. A water supply means 3 is connected to the separation tank 2, and the end of the water supply means 3 opens to the separation tank 2 as a water supply port 7. The water supply means 3 is provided with a micro-bubble generator 4, and is configured to be able to supply bubbles from the water supply port 7. Further, a coal ash supply means 5 is connected to the separation tank 2, and the end of the coal ash supply means 5 opens to the separation tank 2 as a coal ash supply port 8.

The separation tank 2 is a tank for separating unburned carbon contained in coal ash into coal ash and unburned carbon. The upper part of the separation tank 2 is preferably cylindrical. The lower portion of the separation tank 2 is provided with a conical trapezoidal portion having a side portion 6 narrowed downward from the cylindrical portion having a cylindrical shape, from the viewpoint of facilitating the generation of a swirling flow in the lower portion of the separation tank 2. Is preferable.

As will be described later, the water supply port 7 is provided on the side portion 6 narrowed downward, and the vicinity of the water supply port 7 of the water supply means 3 can supply water along the inner wall of the side portion 6. Since it is provided in any direction, a swirling flow is likely to occur in the lower part of the separation tank 2. As a result, the contents of the separation tank 2 tend to be more easily agitated, and unburned carbon tends to float upward.

Further below the conical trapezoidal portion of the separation tank 2, a cylindrical shape can be formed. The diameter of the cylindrical portion below the conical trapezoidal portion can be smaller than the diameter of the cylindrical portion above the conical trapezoidal portion.

The distance from the horizontal cross section of the separation tank 2 including the center of the water supply port 7 to the horizontal cross section of the separation tank 2 including the center of the coal ash supply port 8 and the cylindrical portion above the conical trapezoidal portion of the separation tank 2. The ratio to the diameter (cross-sectional distance / cylinder diameter) is preferably 10/44 or more, and more preferably 20/44 or more. If the ratio is less than 10/44, it becomes difficult to supply bubbles to the lower part of the separation tank 2, and it tends to be difficult to reduce the residual amount of unburned carbon.

The distance from the horizontal cross section of the separation tank 2 including the center of the water supply port 7 to the horizontal cross section of the separation tank 2 including the center of the coal ash supply port 8 and the cylindrical portion above the conical trapezoidal portion of the separation tank 2. The ratio to the diameter (cross-sectional distance / cylinder diameter) is preferably 56/44 or less, and more preferably 44/44 or less. When the ratio exceeds 56/44, the required amount of water increases and the economic efficiency tends to decrease.

The dimensions of the separation tank 2 are not particularly limited, but for example, in the cylindrical portion above the conical trapezoidal portion of the separation tank 2, the ratio of the height of the cylindrical portion to the diameter of the cylindrical portion (cylindrical height / cylinder). Diameter) is preferably preferred.

In the cylindrical portion above the conical trapezoidal portion of the separation tank 2, the ratio of the height of the cylindrical portion to the diameter of the cylindrical portion (cylindrical height / cylindrical diameter) is preferably 35/60 or more. More preferably, it is 50/50 or more. When the ratio (cylinder height / cylinder diameter) is less than 35/60 (for example, when the diameter of the cylinder portion becomes large), the flow velocity near the center of the swirling flow decreases, and unburned carbon floats. Tends to be difficult or difficult to stir coal ash.

The ratio (cylindrical height / cylindrical diameter) between the height of the cylindrical portion and the diameter of the cylindrical portion is preferably 80/20 or less, and more preferably 70/30 or less. When the ratio (cylinder height / cylinder diameter) exceeds 80/20 (for example, when the height of the cylinder portion increases), the speed of the swirling flow increases and the sedimentation of coal ash tends to be slow. As a result, the standing time has to be lengthened, and the economic efficiency of coal ash cleaning tends to decrease.

Further, regarding the dimensions of the separation tank 2, for example, assuming a conical shape formed by extending the narrowed side of the conical trapezoid, the height of the cone and the diameter of the bottom surface of the cone (diameter of the cylinder). It is desirable to optimize the ratio with.

The ratio of the height of the cone to the diameter of the bottom surface of the cone (cone height / cylinder diameter) is preferably 12/44 or more, and more preferably 16/44 or more. When the ratio (cone height / cylinder diameter) is less than 12/44 (for example, when the diameter of the bottom surface of the cone becomes large), the swirling flow is less likely to occur near the upper part of the separation tank 2, so that it is not burned. It tends to be difficult to levitate carbon and to agitate coal ash.

The ratio of the height of the cone to the diameter of the bottom surface of the cone (cone height / cylinder diameter) is preferably 38/44 or less. When the ratio (cone height / cylinder diameter) exceeds 38/44 (for example, when the height of the cone is increased), the swirling flow is less likely to occur in an upward spiral, so that unburned carbon is levitated. It tends to be difficult and difficult to stir the coal ash.

The water supply means 3 is a means for supplying new water to the separation tank 2. Here, the "new water" is not the water supplied by circulating the water already supplied in the separation tank 2 as it is, but is newly supplied to the separation tank 2 from the water stored in the tank, the water supply, or the like. Means water.

The water supply means 3 can be configured to supply the water previously stored in the tank by using a water supply pump or the like. This is possible because the separator 1 does not require a large amount of water to remove unburned carbon. The water supply means 3 may be connected to the tap water to supply tap water.

The vicinity of the water supply port 7 of the water supply means 3 is in a direction tangential to the circumference of the separation tank 2, and the swirling flow is strengthened by the force of supplying water from the water supply port 7 to the separation tank 2. It is preferable that the water is provided in such a direction that the water can be formed.

The water supply port 7 is preferably provided in a portion having a conical trapezoidal shape. Further, the position of the water supply port 7 is preferably a position higher than the height at which coal ash is deposited. When washing 20 kg of coal ash, the volume of the coal ash is about 10 L, and only the coal ash with a large particle size is settled and deposited. Therefore, a volume of about 3 L can be secured below the position of the water supply port 7. It is preferable to provide the water supply port 7 at the position.

Further, inside the separation tank 2, a pipe or the like is provided as a water supply means from the upper part to the lower part of the separation tank 2, and the end of the pipe or the like is the inner wall of the side portion 6 narrowed toward the lower side of the separation tank 2. It may be configured so that water can be supplied along the circumferential direction.

A plurality of water supply means 3 may be provided. When a plurality of water supply means 3 are provided, the heights of the plurality of water supply ports 7 may be the same or different. However, it is desirable that the water supply port 7 is provided in such a manner that the swirling flow is not obstructed, that is, the swirling flow can be strengthened by the force of the water supply pump supplying water to the separation tank 2.

The micro-bubble generator 4 is a bubble supply means for supplying bubbles to the separation tank 2. By supplying the bubbles from the lower part of the separation tank 2, the bubbles can be brought into contact with the unburned carbon contained in the fine coal ash, so that the unburned carbon is easily floated and separated, and the unburned carbon remains. The amount can be further reduced.

It is preferable that the micro-bubble generator 4 has a mode in which bubbles can be supplied from the water supply port 7. With the above configuration, the water flow generated inside the separation tank 2 facilitates the diffusion of bubbles, the bubbles easily come into contact with the unburned carbon contained in the coal ash, and the unburned carbon is easily removed. Further, when the micro-bubble generator 4 is incorporated in the water supply path, water is supplied to the micro-bubble generator 4, so that water containing fly ash and unburned carbon is supplied to the micro-bubble generator 4. Unlike the case, the microbubble generator 4 can exhibit the original performance (particle size and total number of generated microbubbles, etc.). The function of microbubbles is to adsorb to unburned carbon and give buoyancy, and the more microbubbles adhere to unburned carbon, the higher the separation (floating) speed of fly ash and unburned carbon tends to be. .. By incorporating the microbubble generator 4 in the water supply path, the concentration of the microbubbles in the liquid becomes high, and as a result, the fly ash and the non-fly ash are shortly after the water supply to the separation tank 2 is stopped. Separation of fuel carbon is completed, and most of the unburned carbon can be collected in the light layer (upper layer). In addition, instead of supplying the air bubbles from the water supply port 7, the air bubbles may be supplied from the bottom portion of the separation tank 2 or the side portion 6 narrowed downward.

The type of bubble supply means for supplying bubbles to the mixture transferred to the separation tank 2 is not particularly limited, but for example, in addition to the microbubble generator 4, a bubble generator, an orifice type generator, or the like can be used. ..

The coal ash supply means 5 is a means for supplying coal ash to the separation tank 2. It is preferable that the vicinity of the coal ash supply port 8 of the coal ash supply means 5 is provided in a direction tangential to the circumference of the separation tank 2. Further, the direction in the vicinity of the coal ash supply port 8 of the coal ash supply means 5 is such that the coal ash slurry can be supplied to the inside of the separation tank 2 without weakening the swirling flow generated inside the separation tank 2. Is preferable.

The position of the coal ash supply port 8 is preferably higher than that of the water supply port 7. Further, the position of the coal ash supply port 8 is preferably a position where the volume below the coal ash supply port 8 is 28 L or more (about 1/4 of the volume of the contents of the separation tank 2). By satisfying the above positional relationship, coal ash tends to be easily dispersed, easily in contact with air bubbles, and easily reduced in the amount of unburned carbon.

Further, the position of the coal ash supply port 8 is preferably a position where the volume below the coal ash supply port 8 is 55 L or less (about ½ of the volume of the contents of the separation tank 2). By satisfying the above positional relationship, the stirring time of coal ash and the supply time of bubbles are secured, and the amount of unburned carbon tends to be reduced.

It is preferable that the coal ash supply port 8 is installed at a position lower than the liquid level when the water supply is stopped. If the installation position of the coal ash supply port 8 is higher than the liquid level of the contents of the separation tank 2, the coal ash slurry repels when the coal ash slurry is charged, and the coal ash slurry is repelled on the inner wall above the separation tank 2. It may adhere and it may not be possible to sufficiently remove unburned carbon.

The coal ash supply port 8 is provided at a position higher than the water supply port 7. The coal ash supply port 8 may be provided in a cylindrical portion formed in the upper part of the separation tank 2 or may be provided in the lower part of the separation tank 2 as long as the position is higher than the water supply port 7. It may be provided on the side portion 6 that is narrowed downward.

Further, inside the separation tank 2, a pipe or the like is provided as a coal ash supply means from the upper part to the lower part of the separation tank 2, and the end of the pipe or the like is narrowed toward the lower side of the separation tank 2 to the inner wall of the side portion 6. It may be configured in a direction in which the coal ash slurry can be supplied along the circumferential direction of the above. In this case as well, the direction near the end of the pipe or the like as the coal ash supply means should be such that the coal ash slurry can be supplied to the inside of the separation tank 2 without weakening the swirling flow generated inside the separation tank 2. Is preferable.

In addition, the coal ash slurry may be supplied all at once from the opening at the upper part of the separation tank 2 without providing the coal ash supply means 5.

Although it is possible to put the coal ash into the separation tank 2 as it is instead of supplying the coal ash slurry, the coal ash is less likely to be mixed with the water supplied to the separation tank 2. Not preferred.

A plurality of coal ash supply means 5 may be provided. When a plurality of coal ash supply means 5 are provided, the heights of the plurality of coal ash supply ports 8 may be the same or different.

By charging the coal ash slurry from a position higher than the height of the water supply port 7, the coal ash descends from above and bubbles are supplied from below. That is, since the rising bubbles come into contact with the falling coal ash, the unburned carbon adsorbed with oil is likely to be raised by the bubbles. Therefore, the contents of the separation tank 2 can be more reliably separated into a layer containing water and coal ash and a light layer containing unburned carbon adsorbed with oil. It becomes easy to reduce the residual amount. In addition, the time and electric power required to separate unburned carbon and coal ash can be reduced.

Further, the excellent performance of the separation device 1 shown in FIG. 1 can be explained by comparison with, for example, the separation device 30 as shown in FIG. The separation device 30 shown in FIG. 4 sucks coal ash deposited from the coal ash suction port 42 and discharges the coal ash from the coal ash discharge port 43 to circulate the coal ash in the separation tank 31. The ash circulation path 41 is provided. Further, the separation device 30 includes a water circulation path 51 that circulates water in the separation tank 31 by sucking water from the water suction port 52 and discharging water containing microbubbles from the water discharge port 53. The separation device 30 is a device that agitates water, oil, and coal ash in the separation tank 31 to reduce unburned carbon contained in the coal ash according to the above configuration.

In the separation device 30 shown in FIG. 4, the water suction port 52 may suck unburned carbon floating toward the liquid surface of the separation tank 31 or unburned carbon floating on the liquid surface, and is not yet available. The fuel carbon was miniaturized, which sometimes reduced the removal rate of unburned carbon. In addition, the water circulation pump 54 may be easily deteriorated by the mixing of unburned carbon, or the coal ash circulation pump 44 may be easily deteriorated by coal ash. Furthermore, it may take a long time to reduce unburned carbon and energy consumption may increase.

On the other hand, the separation device 1 shown in FIG. 1 does not circulate the water already supplied into the separation tank 2, but is inside the separation tank 2 such as water stored in the tank or water newly supplied from the water supply. It supplies new water that has not been supplied to. Therefore, the removal rate of unburned carbon can be increased without miniaturizing the unburned carbon. In addition, unburned carbon does not enter the pump that supplies water, and the operating time of the pump that supplies water can be shortened, so that deterioration of the pump that supplies water can be suppressed. .. As a result of the above effects, it becomes possible to realize energy saving by removing unburned carbon in a short time.

Further, in the separation device 30, there is a problem that coal ash and unburned carbon remain inside the coal ash circulation path 41 and the water circulation path 51, and the recovery efficiency of the coal ash itself is lowered. On the other hand, since the separation device 1 does not use a circulation path such as a coal ash circulation path 41 or a water circulation path 51, there is an advantage that the recovery efficiency of coal ash is unlikely to decrease.

(How to use the separator)
[Step (B1)]
First, the mixture obtained in the step (A) described later is transferred to a slurrying container to form a coal ash slurry having a coal ash content of 25 to 65% by mass. When the concentration of the coal ash slurry exceeds 65% by mass, the viscosity of the coal ash slurry becomes too high, and it tends to be difficult to supply the coal ash slurry to the separation tank 2 by the coal ash supply pump. When the concentration of the coal ash slurry is less than 25% by mass, the amount of water becomes too large, the concentration of bubbles in the separation tank 2 decreases, and it becomes difficult for the bubbles and unburned carbon to come into contact with each other, resulting in coal ash. Cleaning efficiency tends to decrease. In addition, in the step (A), it is possible to incorporate and carry out the step (B1). For example, water may be added to the mixture and stirred in the coal ash stirrer to form a slurry without transferring the mixture after stirring in the coal ash stirrer to the slurrying container.

[Step (B2)]
First, after operating the water supply pump of the micro bubble generator 4 of the separation device 1, the pressure in the pipe through which the water discharged from the water supply pump flows is adjusted to the opening degree of the valve on the downstream side of the water supply pump. , To the specified pressure. Next, the stop valve on the upstream side of the pump is adjusted to supply air into the pipe from the air inlet located upstream of the water supply pump, and prepare to supply water containing microbubbles. For example, when the total volume of the coal ash slurry and water to be charged into the separation tank 2 (hereinafter referred to as "the volume of the contents to be charged into the separation tank") is 100 L, the flow rate is 2 L / min. It is preferable to supply air and prepare to supply water containing microbubbles. During the preparation, water is discharged from the branch point between the microbubble generator 4 and the separation tank 2.

The flow rate of water supplied from the water supply means 3 for 1 minute is preferably adjusted according to the size of the separation tank 2. For example, when the volume of the contents to be charged into the separation tank is 100 L, the flow rate of water supplied from the water supply means 3 for 1 minute is preferably 9 L / min or more, and is preferably 13 L / min or more. Is more preferable. If the flow rate of water supplied from the water supply means 3 for 1 minute is less than 9 L / min with respect to the volume of the contents to be charged into the separation tank of 100 L, the momentum of the swirling flow is weakened and unburned carbon is used. It tends to be difficult to reduce the residual amount. Further, for example, when the volume of the contents to be charged into the separation tank is X (L), the flow rate of water supplied from the water supply means 3 for 1 minute is X × 9/100 (L / min) or more. It is preferably X × 13/100 (L / min) or more, and more preferably X × 13/100 (L / min) or more.

The flow rate of water supplied from the water supply means 3 for 1 minute is preferably 28 L / min or less, and more preferably 19 L / min or less, with respect to a volume of 100 L of the contents to be charged into the separation tank. .. If the flow rate of water supplied from the water supply means 3 for 1 minute exceeds 28 L / min with respect to the volume of the contents to be charged into the separation tank of 100 L, the momentum of water supply becomes too strong and the swirling flow. Speed increases. As a result, the floating of unburned carbon is delayed, the time until stirring is stopped in the separation tank 2 becomes long, and the separation of unburned carbon tends to be delayed. Further, for example, when the volume of the contents to be charged into the separation tank is X (L), the flow rate of water supplied from the water supply means 3 for 1 minute is X × 28/100 (L / min) or less. It is preferably X × 19/100 (L / min) or less, and more preferably X × 19/100 (L / min) or less.

After adjusting the flow rate of water supplied from the water supply means 3 for 1 minute, the diameter of the bubbles supplied from the microbubble generator 4 is adjusted. The bubble diameter of the bubbles supplied from the micro-bubble generator 4 is preferably 5 to 50 μm in diameter, and more preferably 10 to 40 μm in diameter. When the bubble diameter of the supplied bubble is less than 5 μm, the bubble diameter becomes a nanobubble region, and the force for floating oil and exfoliated unburned carbon tends to decrease. When the bubble diameter of the supplied bubble exceeds 50 μm, the bubble is less likely to be adsorbed on the unburned carbon, so that the effect of floating the oil or the peeled unburned carbon tends to be reduced.

When the volume of the contents to be put into the separation tank is 100 L, after about 30 L of water containing microbubbles is accumulated in the separation tank 2, the coal ash supply pump of the coal ash supply means 5 is operated to the separation tank 2. Supply coal ash slurry. When the volume of the contents to be put into the separation tank is X (L), the supply of coal ash slurry is started after water containing microbubbles is accumulated in the separation tank by X × 10/100 (L) or more. It is more preferable to start the supply of the coal ash slurry after X × 25/100 (L) or more is accumulated. If the supply of coal ash slurry is started with a small amount of water in the separation tank, the amount of microbubbles tends to be insufficient when the slurry is supplied. It is preferable to start supplying the coal ash slurry when the amount of water containing microbubbles in the separation tank is X × 60/100 (L) or less, and the amount of water containing microbubbles is X × 35/100 (L). ) It is more preferable to start supplying the coal ash slurry below. If the supply of coal ash slurry is started with a large amount of water in the separation tank, it is necessary to immediately stop the supply of water after the slurry supply is completed, and there is a tendency that sufficient time for separation and ascent of the layer and unburned carbon cannot be obtained. It is in.

The flow rate of the coal ash slurry supplied from the coal ash supply means 5 for 1 minute is preferably adjusted according to the size of the separation tank 2. The flow rate of the coal ash slurry supplied from the coal ash supply means 5 for 1 minute is preferably 9 L / min or more, and is 27 L / min or more, with respect to the volume of the contents to be charged into the separation tank of 100 L. Is more preferable. If the flow rate of the coal ash slurry supplied from the coal ash supply means 5 for one minute is less than 9 L / min with respect to the volume of the contents to be charged into the separation tank of 100 L, before the supply of the coal ash slurry is completed. There is a tendency for water to be exhausted and processing power to be wasted. Further, for example, when the volume of the contents to be charged into the separation tank is X (L), the flow rate of the coal ash slurry supplied from the coal ash supply means 5 for 1 minute is X × 9/100 (L / min). ) Or more, and more preferably X × 27/100 (L / min) or more.

The flow rate of the coal ash slurry supplied from the coal ash supply means 5 for 1 minute is preferably 55 L / min or less, and 37 L / min or less, with respect to the volume of the contents to be charged into the separation tank of 100 L. Is more preferable. When the flow rate of the coal ash slurry supplied from the coal ash supply means 5 for 1 minute exceeds 55 L / min with respect to the volume of the contents to be charged into the separation tank 100 L, the coal ash supply port 8 enters the separation tank 2. The momentum of supplying the coal ash slurry becomes too strong, and the time required for separating the unburned carbon and the coal ash tends to be long. Further, for example, when the volume of the contents to be charged into the separation tank is X (L), the flow rate of the coal ash slurry supplied from the coal ash supply means 5 for 1 minute is X × 55/100 (L / min). ) Or less, more preferably X × 37/100 (L / min) or less.

When a plurality of coal ash supply means 5 are provided, it is preferable that the flow rate per one is smaller than the above flow rate.

When supplying the coal ash slurry, water containing microbubbles is supplied at the same time, but the liquid level of the water in the separation tank rises with the passage of time, so the supply rate of the coal ash slurry must be controlled. For example, the supply amount per unit time, that is, the flow rate is reduced. By controlling the supply rate of the coal ash slurry, it is possible to make the flow rate of the coal ash slurry constant, and it is preferable to control the supply rate of the coal ash slurry so that the flow rate becomes constant. The supply amount of the coal ash slurry is preferably a certain ratio or less with respect to the volume of the separation tank, and the amount of coal ash is preferably 30 kg or less with respect to 100 L of water. When cleaning coal ash having a high ignition loss, it is preferable to reduce the supply amount of the coal ash slurry for the supplied microbubbles and increase the supply amount of the microbubbles for the coal ash slurry.

Immediately after the coal ash slurry has been supplied, the coal ash supply pump is stopped and the valve incorporated between the coal ash supply pump and the separation tank 2 is closed. When the contents in the separation tank 2 reach 100 L due to the supply of water, the microbubble generator 4 is stopped and the valve between the microbubble generator 4 and the separation tank 2 is closed.

The concentration of coal ash in the contents of the separation tank 2 is preferably 5% by mass or more, and more preferably 10% by mass or more. If the concentration of coal ash in the contents of the separation tank 2 is less than 5% by mass, the economic efficiency of coal ash cleaning tends to be impaired.

The concentration of coal ash in the contents of the separation tank 2 is preferably 30% by mass or less, more preferably 25% by mass or less. If the concentration of coal ash in the contents of the separation tank 2 exceeds 30% by mass, the coal ash and unburned carbon tend to be unable to be sufficiently separated.

After stopping the micro-bubble generator 4, the contents of the separation tank 2 are allowed to stand, and the contents of the separation tank 2 are divided into a light layer containing unburned carbon adsorbed with oil and a multi-layer containing water and coal ash. Separate things. Since most of the oil used in the step (A) described later is adsorbed on unburned carbon, the layer contains almost no oil.

The standing time of the contents of the separation tank 2 is preferably 2 to 30 minutes, more preferably 4 to 20 minutes. If the standing time of the contents of the separation tank 2 is less than 2 minutes, the turning of the contents of the separation tank 2 is not completed, so that the light layer and the multi-layer tend not to be sufficiently separated. When the standing time of the contents of the separation tank 2 exceeds 30 minutes, the separation between the light layer and the multi-layer is almost in equilibrium, and the work efficiency tends to decrease.

After separating the contents of the separation tank 2 into a light layer and a multi-layer, the coal ash deposited in the lower part of the separation tank 2 can be recovered by opening the discharge port 9 provided in the lower part of the separation tank 2. Further, after removing water from the lower part of the separation tank 2, the light layer accumulated in the upper part of the separation tank 2 can be collected in another recovery container from the lower part of the separation tank 2. Alternatively, it may be collected from the upper part of the separation tank 2.

The method for separating and recovering the unburned carbon adsorbing the oil contained in the light layer into the oil and the unburned carbon is not particularly limited, but for example, a known device such as a filter press or a centrifuge may be used. can. Since the recovered oil can be used again for cleaning coal ash, the cleaning cost can be further reduced. Further, the recovered unburned carbon can be easily disposed of as industrial waste because the water content is reduced to about 15% and the content of heavy metals is low by dehydrating the recovered carbon with a filter press.

The method for separating and recovering the water and coal ash contained in the layer is not particularly limited, but for example, a known device such as a drainer conveyor, a filter press machine, or a centrifuge can be used. Since the recovered water can be used again for cleaning coal ash, the cleaning cost can be further reduced. Further, the recovered coal ash can be used as an admixture for ready-mixed concrete, a fine aggregate, or the like after being dried by a known method such as being transferred to a vibrating conveyor and dried with warm air.

The reduced residual amount of unburned carbon is preferably 2.0% by mass or less, more preferably 1.5% by mass or less, and further preferably 1.0% by mass or less. If the reduced residual amount of unburned carbon exceeds 2.0% by mass, the amount of admixture used to adjust the fluidity and air content of fresh concrete increases, or the amount of admixture added. The strength of concrete tends to fluctuate due to problems such as fluctuations in fluidity and air volume. In addition, fluctuations in the strength of concrete may cause cracks in the manufactured concrete. Since cracks in concrete need to be repaired by human work, concrete that is less likely to crack is desired in the construction industry and the civil engineering industry.

The method for measuring the residual amount of unburned carbon is not particularly limited, but can be calculated, for example, by measuring the ignition loss of coal ash by the method specified in JIS A 6201: 1999.

[Step (A)]
As described above, before the step (B1) and the step (B2), the coal ash containing unburned carbon is impregnated with water and oil to appropriately adjust the solid content concentration, and then the obtained mixture is obtained. By performing the step (A) of stirring the above, the residual amount of unburned carbon can be significantly reduced.

The solid content concentration in the step (A) is preferably 65 to 90% by mass, more preferably 70 to 90% by mass, and even more preferably 70 to 85% by mass. By setting the concentration of the solid content in the above range, the amount of water and oil used can be suppressed, so that the cleaning cost of coal ash tends to be easily reduced.

When the concentration of the solid content is less than 65% by mass, the amounts of water and oil are relatively large, the share by stirring is difficult to be applied, and the efficiency of removing unburned carbon tends to decrease. When the solid content concentration exceeds 90% by mass, the amount of water and oil becomes relatively small, it becomes difficult for water and oil to spread on the surface of coal ash, and the efficiency of removing unburned carbon tends to decrease. ..

In the step (A), the oxide mainly composed of silicon or aluminum and the oily unburned carbon sticking to the surface of the glass are peeled off by the high affinity with the oil in the mixture and the strong stirring power of the stirrer. And removed from the surface of the coal ash. Alternatively, oil is attached to the independent unburned carbon particles to impart hydrophobicity.

In the step (A), the amount of oil in the mixture is preferably 0.15% by mass or more, more preferably 0.2% by mass or more, and further preferably 0.3% by mass or more. It is preferably 0.4% by mass or more, and particularly preferably 0.4% by mass or more. Further, it is more preferably 0.5% by mass or more, further preferably 0.8% by mass or more, and particularly preferably 1.3% by mass or more. Further, in the step (A), the amount of oil in the mixture is preferably 10% by mass or less, more preferably 7.0% by mass or less, and further preferably 6.0% by mass or less. It is preferably 4.0% by mass or less, particularly preferably 3.8% by mass or less, and most preferably 2.0% by mass or less. By setting the amount of oil in the above range, the amount of oil used can be suppressed, so that the cleaning cost of coal ash tends to be easily reduced.

When the amount of oil in the mixture is less than 0.15% by mass, the amount of oil that can adhere to unburned carbon decreases, so that the efficiency of removing unburned carbon tends to decrease. When the amount of oil in the mixture exceeds 10% by mass, the amount of oil exceeds the amount required for removing unburned carbon, which tends to be economically wasteful.

The type of oil that can be used in the step (A) is not particularly limited, but for example, kerosene, kerosine oil, recycled kerosene or kerosine oil, palm oil, coconut oil, pine oil, edible oil, or edible oil. Waste cooking oil, which is recycled oil, can be used. In addition, these oils may be used alone or in combination of two or more.

When two or more kinds of oils are used in combination, a combination of a hydrocarbon oil such as kerosene or kerosine oil and a fatty oil such as palm oil, pine oil or edible oil having a carboxyl group is preferable. Among such oil combinations, a combination of 2 to 4 kinds of oils selected from the group consisting of kerosene, palm oil, pine oil and edible oil, particularly a combination of kerosene and edible oil is preferable.

Further, it is more preferable to mix the mixed oil and water obtained by the above combination with coal ash after undergoing an emulsification step of stirring in advance with a mixer or the like to emulsify. By mixing the mixed oil and water with the coal ash after the emulsification step, the oil can be uniformly dispersed in the step (A) in a short time.

The type of edible oil is not particularly limited, but is, for example, salad oil, rapeseed oil, corn oil, sunflower oil, olive oil, sesame oil, soybean oil, walnut oil, hazelnut oil, macadamia nut oil, perilla oil, grape seed oil, borage oil, pumpkin. Seed oil, camellia oil, red flower oil, cottonseed oil, teaseed oil, rice bran oil, flaxseed oil, peanut oil, wheat germ oil and the like.

The oil used in the step (A) may have a hydrophobicity such that the hydrophobic group can interact with the unburned carbon on the surface of coal ash by intermolecular force. It is considered that the purity and the like do not significantly affect the removal efficiency of unburned carbon. Therefore, recycled oil can also be used as the oil used in the step (A). Recycled oil means oil that has been used at least once for edible or industrial purposes. By using recycled oil, the cost of cleaning coal ash can be further reduced.

The type of recycled oil is not particularly limited, but for example, kerosene, kerosine oil, palm oil, palm oil, pine oil, edible oil and the like can be recycled and used. By using recycled oil, it is possible to reduce the cost required for the process (A) and also reduce the burden on the environment.

In the step (A), the amount of water in the mixture is preferably 5 to 30% by mass, more preferably 10 to 27% by mass, and even more preferably 12 to 25% by mass. When the amount of water in the mixture is less than 5% by mass, it becomes difficult for water to spread on the surface of coal ash, and the efficiency of removing unburned carbon tends to decrease. When the amount of water in the mixture exceeds 30% by mass, the frequency of contact between unburned carbon and oil decreases, and it becomes difficult to take a share by stirring, so that the efficiency of removing unburned carbon tends to decrease. It is in.

The function of the coal ash agitator used in the step (A) is not particularly limited as long as it can sufficiently agitate the solid content and the water containing oil and can apply a strong share to the surface of the coal ash. .. As a coal ash agitator having the above-mentioned functions, a known agitator can be used. Machines, planetary mixers, homomixers, homodispers, henschel mixers, Banbury mixers, ribbon mixers, concrete mixers, horizontal uniaxial or biaxial forced kneaders, or automatic weighing mixing units.

By using the above-mentioned coal ash stirring device, it is possible to increase the stirring power per unit volume and to perform stirring and washing of coal ash in a short time. In addition, it becomes easier to simplify the cleaning equipment and reduce the cleaning cost. In particular, among coal ash agitators, twin-screw smelting extruders can apply a strong share and tend to be able to remove unburned carbon more effectively.

[Coal ash cleaning system]
The coal ash cleaning system of the present invention will be described with reference to FIG. FIG. 3 is a conceptual diagram of a coal ash cleaning system according to an embodiment of the present invention.

A predetermined amount of water with respect to the coal ash is charged into the emulsification stirring device 14 from the water charging device 11, and a predetermined amount of oil with respect to the coal ash is charged into the emulsification stirring device 14 from the oil charging devices 12 and 13. The added water and oil are stirred by the emulsification stirring device 14 to emulsify. It should be noted that this emulsification step can be omitted.

FIG. 3 illustrates a mode in which a predetermined amount of oil is charged from the oil charging device 12 and a predetermined amount of recycled oil is charged from the oil charging device 13, but the oil and the recycled oil are charged from the same oil charging device. It may be a mode of charging. When two or more kinds of oil are used, an oil charging device may be provided according to the number of types of oil, or a plurality of oils may be charged from one oil charging device.

The coal ash containing unburned carbon is charged into the coal ash stirring device 16 from the coal ash charging device 15, and the emulsified and agitated water and oil are charged into the coal ash stirring device 16 from the emulsification stirring device 14.

The water, oil and coal ash charged into the coal ash agitator 16 are stirred by the coal ash agitator 16 with a strong share. The mixture does not need to be formed in the coal ash agitator 16, and the coal ash, water and oil are mixed in an arbitrary container, and then the obtained mixture is agitated by the coal ash agitator 16. It may be a mode to be used.

The mixture stirred by the coal ash agitator 16 is charged into the slurrying container 18, and water is added to the slurrying container 18 from the slurrying water charging device 17 to form a slurry. Alternatively, water may be added from the slurrying water input device 17 to the mixture after stirring by the coal ash stirring device 16 and stirred by the coal ash stirring device 16 to form a slurry. Further, after stirring with the coal ash stirring device 16, water is added to the coal ash stirring device 16 to form a slurry as shown without using the slurrying container 18, and the obtained coal ash slurry is separated into a separation tank. It may be supplied to 21.

Before supplying the coal ash slurry from the slurrying container 18 to the separation tank 21, water and bubbles are supplied to the separation tank 21. Water is supplied from the water supply device 19 to the separation tank 21. The bubbles are supplied from the microbubble generator 20 to the separation tank 21 together with water.

After a predetermined amount of water and bubbles are supplied to the separation tank 21, the coal ash slurry is transferred from the slurrying container 18 to the separation tank 21 to the separation tank 21, gently stirred, and then allowed to stand. The stirring is gently performed by the swirling flow in the separation tank 21. As the separation tank 21, it is preferable to use the separation device 1 or the like shown in FIG.

The contents are allowed to stand to separate the contents into a layer containing water and coal ash and a light layer containing unburned carbon adsorbed with oil, and then the layer and the light layer are removed, respectively. In addition, instead of supplying water from the water supply device 19 to the separation tank 21, it may be a mode in which water is branched from the water charging device 11 or the slurryed water charging device 17 to supply water to the separation tank 21.

The discharge port provided on the bottom surface of the separation tank 21 is opened, and the multi-layer containing water and coal ash is transferred from the discharge port to the multi-layer filter press machine 22. After the layer is removed, the discharge port of the separation tank 21 is closed so that the light layer is not discharged. In the multi-layer filter press machine 22, the water in the multi-layer is removed, the coal ash is isolated, and the coal ash is transferred to the drying conveyor 23. When the coal ash is dried on the drying conveyor 23, coal ash with a reduced residual amount of unburned carbon can be obtained.

After removing the layer, a light layer containing unburned carbon adsorbed with oil remains in the separation tank 21. The discharge port provided on the bottom surface of the separation tank 21 is opened again, and the light layer is transferred to the light layer filter press machine 24. The light layer transferred to the light layer filter press machine 24 is separated into oil and unburned carbon. The oil separated in the light layer filter press machine 24 may be further transferred to the water / oil separation tank 25 and separated into water and oil.

The oil recovered from the light layer filter press machine 24 or the water / oil separation tank 25 can be charged into the oil charging device 13 and used again for cleaning coal ash.

The water used for washing the coal ash can be recovered from the multi-layer filter press machine 22, the drying conveyor 23, and the water / oil separation tank 25. Tap water or the like is usually used for the water input device 11, the slurry water input device 17, or the water supply device 19, but the recovered water is used as the water input device 11, the slurry water input device 17, or the water supply device. It can be put into 19 or the like and used again for washing coal ash.

A coal ash stirrer that stirs a mixture containing unburned carbon-containing coal ash, water and oil, and a solid content concentration of 65 to 90% by mass as described above, and further water to the stirred mixture. And the coal ash slurry to form a coal ash slurry, and the coal ash slurry was put into a separation tank to which water and air bubbles were supplied, and a layer containing water and coal ash and oil were not adsorbed. It can be a coal ash cleaning system having a separation device for separating into a light layer containing fuel carbon. With the above cleaning system, the removal rate of unburned carbon is increased without making the unburned carbon finer, the deterioration of the pump that supplies water is suppressed, and the unburned carbon is removed in a short time to save energy. While, the coal ash can be washed.

Further, even if a smaller scale device, a cheaper device, or a method having a lower running cost is used, the unburned carbon contained in the coal ash can be reduced more than the conventional one. That is, the coal ash cleaning system of the present invention can reduce unburned carbon contained in coal ash with simpler equipment and lower cleaning cost.

In addition, the coal ash cleaning system of the present invention uses only a small amount of water and a small amount of oil in the step (A), and is a very inexpensive cleaning system. Therefore, if the coal ash is to be washed at the same cost as before, it is possible to add more equipment to that extent, and it is possible to wash a larger amount of coal ash than before. ..

[Oil reuse process]
In the method for producing coal ash of the present invention, the amount of oil used is minimized by recovering the oil used for separating unburned carbon and reusing the recovered oil in step (A). It can be limited to the limit, and further cost reduction can be achieved.

The method for recovering the oil is not particularly limited, and examples thereof include a method for recovering the oil by applying a filter press to a light layer containing the oil. The recovered oil may be further separated into oil and water, then refined and reused.

[Water reuse process]
In the method for producing coal ash of the present invention, the amount of water used is minimized by recovering the water used for separating unburned carbon and reusing the recovered water in the step (A). It can be limited to the limit, and further cost reduction can be achieved.

The method for recovering water is not particularly limited, and examples thereof include a method for recovering water removed by a draining conveyor or a vibrating conveyor from a layer containing water. Further, when the oil and water are recovered from the light layer containing water and then the oil is further refined, the water separated in the step may be recovered.

[Coal ash and concrete]
Since the coal ash produced by the production method of the present invention is difficult to adsorb the water reducing agent and the AE agent, it suppresses a significant decrease in air entrainment when blended in cement, and is derived from the adsorption of the water reducing agent and the AE agent. It is possible to suppress fluctuations in quality. Further, when the coal ash produced by the production method of the present invention is blended with cement to produce fresh mortar or fresh concrete, the consistency of the fresh mortar or fresh concrete is lowered and the workability is improved. Further, the mortar and concrete obtained by hardening the above-mentioned fresh mortar and fresh concrete have high compressive strength due to the pozzolan effect and the like due to the blending of coal ash. Further, since the color of coal ash with reduced unburned carbon is whiter than that of unwashed coal ash, there is an advantage that the color does not turn black even if a considerable amount is added to the cement.

The miscibility of coal ash with the ready-mixed concrete is preferably 5 to 30% by mass, more preferably 10 to 20% by mass in the internal split method. When the amount of coal ash mixed with the ready-mixed concrete is less than 5% by mass, the effect of adding the coal ash is reduced, the compressive strength of the concrete is lowered, and the concrete tends to be easily cracked. When the miscibility of coal ash with the ready-mixed concrete exceeds 30% by mass, the fluidity of the ready-mixed concrete increases, but the progress of neutralization of the concrete becomes rapid, so that the long-term strength tends to decrease.

Hereinafter, examples of the present invention will be described, but the present invention is not limited thereto.

[Measurement method of unburned carbon residual amount]
The amount of unburned carbon remaining in the coal ash can be calculated by measuring the ignition loss of the coal ash. The ignition loss of coal ash can be measured by the method specified in JIS A 6201: 1999.

In the ignition loss test, about 1 g of coal ash as a sample was correctly weighed up to 0.1 mg in a crucible (capacity 15 ml) specified in JIS R 1301, and heated in an electric furnace adjusted to 950 to 1000 ° C for 15 minutes. After allowing to cool in a desiccator, weigh the mass and repeat the ignition for another 15 minutes. Ignition weight loss is obtained by subtracting the moisture content from the percentage obtained by dividing the weight loss when the weight becomes constant by the mass of the sample.

In the wet content test, about 50 g of coal ash after filter pressing as a sample is correctly weighed to 0.1 mg in a beaker (100 ml), dried in an electric furnace adjusted to 110 ° C for 24 hours or more, and allowed to cool in a desiccator. After that, the mass was weighed. The percentage of the mass obtained by dividing the difference in mass before and after drying by the mass before drying is the moisture content.

[Separator]
The separation device used in the following examples is the separation device 1 as shown in FIG. The separation device 1 includes a separation tank 2 that separates unburned carbon contained in coal ash into coal ash and unburned carbon. The separation tank 2 is provided with a water supply port 7 of the water supply means 3. Then, the microbubble generator 4 for supplying the microbubbles is incorporated in the water supply pump of the water supply means 3. Further, the separation tank 2 is provided with a coal ash supply port 8 of the coal ash supply means 5 for supplying the coal ash slurry at a position higher than the water supply port 7. The lower part of the separation tank 2 is provided with a conical trapezoidal portion having a side portion 6 narrowed downward, and the vicinity of the water supply port 7 of the water supply means 3 is a conical trapezoidal shape of the lower part of the separation tank 2. It is provided so as to be tangential to the circumference of the side portion 6. The vicinity of the coal ash supply port 8 of the coal ash supply means 5 is provided in the tangential direction with respect to the circumference of the cylindrical portion of the separation tank 2, and is provided so as to face upward by about 5 ° with respect to the horizontal cross section. There is. Further, the vicinity of the water supply port 7 of the water supply means 3 and the vicinity of the coal ash supply port 8 of the coal ash supply means 5 are provided in a direction in which a swirling flow in the same direction is generated by each other's water flow.

Further, in the cylindrical portion above the conical trapezoidal portion of the separation tank 2, the ratio of the height of the cylindrical portion to the diameter of the cylindrical portion (cylindrical height / cylindrical diameter) is 60/44. In addition, assuming a conical shape formed by extending the narrowed side of a conical trapezoid, the ratio of the height of the cone to the diameter of the bottom surface of the cone (cone height / cylinder diameter) is 38. It is / 44. Further, the distance from the horizontal cross section of the separation tank 2 including the center of the water supply port 7 to the horizontal cross section of the separation tank 2 including the center of the coal ash supply port 8 and the cylinder above the conical trapezoidal portion of the separation tank 2. The ratio (cross-sectional distance / cylinder diameter) to the diameter of the portion is 31/44.

(Example 1)
Coal ash (residual amount of unburned carbon 4.8% by mass) 5 kg (1 batch) collected from a coal-fired power plant, 1220 ml of water and kerosene (manufactured by Cosmo Oil Co., Ltd., specific gravity 0.8 g / ml) 20 ml and A mixture of 8.2 ml of cooking oil (rapeseed oil and soybean oil) (manufactured by RIKEN Agricultural Chemicals Co., Ltd., edible blended oil, specific gravity 0.8 g / ml) emulsified and stirred with a mixer (manufactured by Matsushita Electric Industrial Co., Ltd., National MX-V350). Was filled in a container (pan) of an Erich mixer (RV-02 manufactured by Japan Eirich Co., Ltd.). The output of the pan drive motor was 0.88 kW, the rotation speed was 66 rpm, the output of the stirring drive motor was 1.8 kW, the rotation speed was 3470 rpm, and the mixture was vigorously stirred for 4 minutes. A similar treatment was further performed on one batch to give a total of about 12.5 kg of a mixture containing coal ash, water, kerosene and cooking oil.

A mixture containing about 12.5 kg of coal ash, water, kerosene, and cooking oil was placed in a plastic container, 12 L of water was added, and then the mixture was stirred using a hand mixer for about 30 seconds to obtain 41% by mass of coal ash. A coal ash slurry was obtained.

Air was supplied to the microbubble generator 4 (MBG20N07CE-1BH manufactured by Nikuni Co., Ltd.) at a speed of 2 L / min to generate microbubbles having an average median diameter of about 20 μm. Water containing the microbubbles was supplied from the water supply port 7 at the bottom of the separation tank 2 at a rate of about 16 L / min. When about 30 L of water was accumulated in the separation tank 2, 24.5 L of the coal ash slurry in the plastic container was supplied into the separation tank 2 from the coal ash supply port 8 at a flow rate of about 32 L / min. After the supply of the coal ash slurry was completed, about 2 L of water was flowed into the coal ash supply means 5 to flush out the residue, and the valve of the coal ash supply means 5 was closed. Water is continuously supplied from the water supply port 7 at a flow rate of about 16 L / min, and when the volume of the contents of the separation tank 2 reaches about 100 L, the water supply is stopped and the micro bubble generator 4 is stopped at the same time. The operation of was also stopped. The time (time for the separation step) from the start of supplying water containing the microbubbles to the separation tank 2 until the water supply was stopped was 7 minutes. The concentration of coal ash in the contents of the separation tank 2 was 9.5% by mass. Since water containing microbubbles is supplied at a rate of about 16 L / min until the volume of the contents together with 24.5 L of coal ash slurry reaches 100 L, the time of the separation step is calculated. It takes less than 5 minutes. As described above, it is presumed that the cause of the difference between the actual separation step time and the calculated separation step time is that the water supply speed to the separation tank 2 decreases due to the water pressure.

After stopping the supply of water, the contents of the separation tank 2 were allowed to stand for 5 minutes. The static contents were separated into a light layer containing unburned carbon adsorbed with oil and a layer containing water and coal ash. The coal ash deposited in the lower part of the separation tank 2 was collected from the discharge port 9 in the lower part of the separation tank 2 by opening the ball valve attached to the lower part of the separation tank 2. Further, after removing water from the lower part of the separation tank 2, the light layer accumulated in the upper part of the separation tank 2 was dropped from the lower part of the separation tank 2 into another collection container for recovery.

The recovered light layer was separated into water and unburned carbon using a filter press device (M8 manufactured by Makino Co., Ltd.). The water content of the recovered unburned carbon was about 15%. The recovered unburned carbon was placed in a dryer and dried in an atmosphere of 110 ° C. for 24 hours.

For the layers, water and washed coal ash were separated from each other using a filter press device (FLP14 manufactured by Makino Iron Works Co., Ltd.). The water content of the separated coal ash was about 16%. The separated coal ash was placed in a dryer and dried in an atmosphere of 110 ° C. for 24 hours. The residual amount of unburned carbon in the dried coal ash was 0.30% by mass. In addition, about 80% or more of the water used for washing the coal ash could be recovered.

(Example 2)
Instead of supplying the coal ash slurry from the coal ash supply means 5, the coal ash slurry was charged from the upper part of the separation tank 2 and immediately stirred with a hand mixer for about 45 seconds, but the coal was obtained by the same method as in Example 1. The ash was treated and the residual amount of unburned carbon was measured. The residual amount of unburned carbon in the coal ash was 0.48% by mass.

The composition and experimental conditions of the mixture in Examples 1 and 2 are summarized in Table 1. The time of the separation step in the table means the time from the start of supplying water to the separation tank to the time when the supply of water is stopped. In the supply angle of the coal ash slurry in the table, "+" indicates a supply angle in which the discharge direction of the coal ash slurry faces upward with respect to the horizontal cross section, and "-" indicates a downward direction with respect to the horizontal cross section. Represents the facing supply angle.

Comparing Example 1 and Example 2, the method of supplying the coal ash slurry is different. In Example 1 in which the coal ash slurry was supplied by the coal ash supply means 5 at a rate of about 32 L / min, the residual amount of unburned carbon after the treatment was 0.30% by mass. On the other hand, in Example 2 in which the coal ash slurry was supplied from the upper part of the separation tank 2 at one time, the residual amount of unburned carbon after the treatment was 0.48% by mass. That is, from the comparison between Example 1 and Example 2, it is better to supply the coal ash slurry by the coal ash supply means 5 at a rate of about 32 L / min than to charge the coal ash slurry from the upper part of the separation tank 2 at once. However, it can be seen that the residual amount of unburned carbon can be effectively reduced.

Next, a comparative example will be described. The separation device used in the following comparative example is a separation device as shown in FIG. The separation device 30 shown in FIG. 4 includes a separation tank 31 capable of separating coal ash and unburned carbon in the mixed liquid. Further, the separation device 30 includes a coal ash circulation path 41 capable of circulating a mixed liquid containing the deposited coal ash. The coal ash circulation path 41 is formed as a flow path connecting the coal ash suction port 42 provided at the lower part of the separation tank 31 and the coal ash discharge port 43 provided at the upper part of the separation tank 31. Further, the separation device 30 includes a water circulation path 51 capable of circulating a mixed liquid containing water. The water circulation passage 51 is formed as a flow path connecting the water suction port 52 provided in the upper part of the separation tank 31 and the water discharge port 53 provided in the lower part of the separation tank 31. The water circulation path 51 is provided with a microbubble generator 55 that supplies bubbles from the lower part of the separation tank 31. The lower part of the separation tank 31 is provided with a conical trapezoidal portion having a side portion narrowed downward. The water discharge port 53 is provided on the side portion of the conical trapezoid of the separation tank 31 so that the vicinity of the water discharge port 53 of the water circulation path 51 faces in the tangential direction with respect to the circumference of the side portion. In addition, the height of the coal ash suction port 42 is equal to or lower than the height of the water discharge port 53.

Further, in the separation device 31, the ratio of the height of the cylindrical portion to the diameter of the cylindrical portion (cylindrical height / cylindrical diameter) is 60/44 in the cylindrical portion above the conical trapezoidal portion of the separation tank 31. ing. In addition, assuming a conical shape formed by extending the narrowed side of a conical trapezoid, the ratio of the height of the cone to the diameter of the bottom surface of the cone (cone height / cylinder diameter) is 38. It is / 44. Further, the distance from the horizontal cross section of the separation tank 31 including the center of the water discharge port 53 to the horizontal cross section of the separation tank 31 including the center of the coal ash suction port 42, and the cylinder above the conical trapezoidal portion of the separation tank 31. The ratio (cross-sectional distance / cylinder diameter) to the diameter of the portion is 27/44. In addition, the height of the coal ash discharge port 43 is provided at a position higher than the height of the water suction port 52. Further, the vicinity of the coal ash discharge port 43 in the coal ash circulation path 41 is provided so as to be oriented perpendicular to the side surface of the separation tank 31.

(Comparative Example 1)
5 kg (1 batch) of coal ash (residual amount of unburned carbon 13.2% by mass) collected from a coal-fired power plant, 750 ml of water, 75 ml of kerosene (manufactured by Cosmo Oil Co., Ltd., specific gravity 0.8 g / ml) and 75 ml in advance. A mixture of 6.5 ml of cooking oil (rapeseed oil and soybean oil) (manufactured by RIKEN Agricultural Chemicals Co., Ltd., edible blended oil, specific gravity 0.8 g / ml) emulsified and stirred with a mixer (manufactured by Matsushita Electric Industrial Co., Ltd., National MX-V350). Was filled in a container (pan) of an Erich mixer (RV-02 manufactured by Japan Eirich Co., Ltd.). The output of the pan drive motor was 0.88 kW, the rotation speed was 66 rpm, the output of the stirring drive motor was 1.8 kW, the rotation speed was 3470 rpm, and the mixture was vigorously stirred for 4 minutes. A similar treatment was further performed on one batch to give a total of about 11.6 kg of the mixture containing coal ash, water, kerosene and cooking oil.

About 100 L of water was stored in the separation tank of the separation device, and the water circulation pump 54 was operated. The pressure of the water circulation pump 54 was adjusted so that the flow rate in the water circulation passage 51 for 1 minute was 18.3 L / min (0.18 times the mixed liquid in the separation tank 31). Further, bubbles having a bubble diameter of about 20 μm generated by the micro bubble generator 55 (MBG20N07CE-1BH manufactured by Nikuni Co., Ltd.) were blown into the separation tank 31 from the water circulation path 51 at a speed of 2 L / min.

The coal ash circulation pump 44 was operated, and water was circulated in the coal ash circulation path 41 so that the flow rate per minute was 30 L / min (0.3 times the mixed liquid in the separation tank 31). Next, a mixture of coal ash containing kerosene, water, and edible oil stirred with an Erich mixer was added from the upper part of the separation tank 31 to prepare a coal ash slurry having a coal ash content of about 10% by mass. The coal ash was circulated together with water at the above flow rate by the coal ash circulation pump 44, and the coal ash slurry was gently stirred for 7.5 minutes. After the above stirring, the operation of the coal ash circulation pump 44 was stopped, and 7.5 minutes later, the operation of the water circulation pump 54 was also stopped. The time (time for the separation step) from the supply of coal ash to the separation tank 31 to the time when the water circulation pump 54 was stopped and the water supply was stopped was 15 minutes. The operating time of the coal ash circulation pump 44 was 7.5 minutes.

After stopping the operation of the water circulation pump 54, the contents of the separation tank 31 were allowed to stand for 5 minutes. The static contents were separated into a light layer containing unburned carbon adsorbed with oil and a layer containing water and coal ash. The coal ash deposited in the lower part of the separation tank 31 was collected from the lower part of the separation tank 31 by opening the ball valve 32 attached to the lower part of the separation tank 31. Further, after removing water from the lower part of the separation tank 31, the light layer accumulated in the upper part of the separation tank 31 was dropped from the lower part of the separation tank 31 into another collection container for recovery.

The recovered layers were separated into water and washed coal ash using a filter press device (FLP14 manufactured by Makino Iron Works Co., Ltd.). The water content at the time of separation was about 16%. The separated coal ash was placed in a dryer and dried with warm air at 110 ° C. for 24 hours. The residual amount of unburned carbon in the dried coal ash was 0.69% by mass.

The recovered light layer was separated into water and unburned carbon using a filter press device (M8 manufactured by Makino Co., Ltd.). The moisture content of the separated unburned carbon was about 15%. The separated unburned carbon was placed in a dryer and dried in an atmosphere of 110 ° C. for 24 hours.
(Comparative Example 2)
A mixture of 5 kg (1 batch) of coal ash (residual amount of unburned carbon 13.2% by mass) collected from a coal-fired power plant and 1000 ml of water, 75 ml of kerosene and 6.5 ml of edible oil was emulsified and stirred with a mixer in advance. A mixture was obtained in the same manner as in Example 1 except that the container (pan) of the Erich mixer was filled. This mixture was treated with coal ash in the same manner as in Comparative Example 1 and the residual amount of unburned carbon was measured. The residual amount of unburned carbon in the coal ash was 0.54% by mass.

(Example 3)
Eich mixer is a mixture of 5 kg of coal ash (residual carbon residue 13.2% by mass) collected from a coal-fired power plant, 1,000 ml of water, 75 ml of kerosene and 6.25 ml of edible oil that have been emulsified and stirred with a mixer. Coal ash was treated in the same manner as in Example 1 except that the mixture was filled in the container (pan) and stirred, and the residual amount of unburned carbon was measured. The residual amount of unburned carbon in the coal ash was 0.50% by mass.

Table 2 summarizes the composition and experimental conditions of the mixtures in Comparative Examples 1 and 2 and Example 3.

Comparing Example 3 and Comparative Example 2, the separation device used for separation is different. In Example 3 using the separation device 1 shown in FIG. 1, it took 7 minutes for the separation step in order to make the residual amount of unburned carbon after the treatment 0.50% by mass, whereas in FIG. In Comparative Example 2 using the separation device 30 described in the above, the separation step required 15 minutes in order to make the residual amount of unburned carbon after the treatment 0.54% by mass. That is, from the comparison between Example 3 and Comparative Example 2, when the separating device 1 is used, the residual amount of unburned carbon can be reduced in about half the time as compared with the case where the separating device 30 is used. You can see that it has become. This is because in the separation device 30, unburned carbon is refined or diffused by the coal ash circulation pump 44, and as a result, it takes time to separate the unburned carbon, whereas in the separation device 1, it takes time. , It is considered that such a demerit does not occur.

Comparing Example 3 and Comparative Example 1, the separation device used for the separation and the amount of water used in the stirring step are different. The amount of water used in the stirring step is 2000 ml in Example 3, whereas it is 1500 ml in Comparative Example 1. That is, Comparative Example 1 has a larger share of coal ash during stirring than Example 3. Nevertheless, in Example 3, the residual amount of unburned carbon after the treatment was 0.50% by mass, and in Comparative Example 1, the residual amount of unburned carbon after the treatment was 0.69% by mass. Further, in Example 3, the separation step takes only 7 minutes, whereas in Comparative Example 1, the separation step takes 15 minutes. That is, from the comparison between Example 3 and Comparative Example 1, the case where the separation device 1 shown in FIG. 1 is used is larger than the case where the separation device 30 shown in FIG. 4 is used with respect to coal ash. It can be seen that the residual amount of unburned carbon can be further reduced in about half the time without applying a share.

Comparing Comparative Example 1 and Comparative Example 2, the amount of water used in the stirring step is different. In Comparative Example 1 in which the amount of water used in the stirring step was small, when the mixture of coal ash was put into the separation tank 21 of the separation device 30, the coal ash was hard to settle and the coal ash was easy to float on the liquid surface. On the other hand, in Comparative Example 2, since the amount of water used in the process was larger than that in Comparative Example 1, coal ash was likely to settle. As a result, it is considered that the residual amount of unburned carbon was reduced in Comparative Example 2 as compared with Comparative Example 1.

(Example 4)
Eich mixer is a mixture of 5 kg of coal ash (residual carbon residue of 8.3%) collected from a coal-fired power plant, 1,250 ml of water, 50 ml of kerosene and 6.25 ml of edible oil mixed in advance with a mixer. Coal ash was treated in the same manner as in Example 1 except that the mixture was filled in the container (pan) and stirred, and the standing time was set to 10 minutes, and the residual amount of unburned carbon was treated. Was measured. The residual amount of unburned carbon in the coal ash was 0.28% by mass. The dry weight of the recovered layer was 7.5 kg.

(Example 5)
The coal ash supply means 5 of the separation device 1 is connected and fixed at a supply angle such that the discharge direction of the coal ash slurry faces downward by 45 ° with respect to the horizontal cross section, except that the method is the same as that of the fourth embodiment. Coal ash was treated and the residual amount of unburned carbon was measured. The residual amount of unburned carbon in the coal ash was 0.22% by mass. The dry weight of the recovered layer was 7.8 kg.

(Example 6)
The coal ash supply means 5 of the separation device 1 is connected and fixed at a supply angle such that the discharge direction of the coal ash slurry faces upward by 30 ° with respect to the horizontal cross section, except that the method is the same as that of the fourth embodiment. Coal ash was treated and the residual amount of unburned carbon was measured. The residual amount of unburned carbon in the coal ash in the layer was 0.21% by mass, and the dry weight was 7.8 kg (referred to as the primary recovered product). The dry weight of the light layer was 2.1 kg (referred to as a secondary recovered product). Further, the layer remaining inside the coal ash supply means 5 was recovered, and the dry weight was measured to be 0.1 kg (referred to as a tertiary recovered product). The total weight of the primary recovered material, the secondary recovered material, and the tertiary recovered material was 10 kg, and almost all of the coal ash charged was recovered.

(Comparative Example 3)
A mixture of 5 kg (1 batch) of coal ash (unburned carbon residual amount 8.3% by mass) collected from a coal-fired power plant and 1250 ml of water, 50 ml of kerosene and 6.5 ml of edible oil previously emulsified and stirred with a mixer. A mixture was obtained in the same manner as in Example 1 except that the container (pan) of the Erich mixer was filled. This mixture was prepared in the same manner as in Comparative Example 1 except that the operating time of the coal ash circulation pump 44 was 6.5 minutes, the operating time of the water circulation pump 54 was 13 minutes, and the standing time was 10 minutes. Was treated, and the residual amount of unburned carbon was measured. The residual amount of unburned carbon in the coal ash was 0.50% by mass, and the dry weight was 6,3 kg (referred to as the primary recovered product). The dry weight of the light layer was 1.8 kg (referred to as a secondary recovered product). Further, when the layers remaining inside the coal ash circulation passage 41 and the water circulation passage 51 were recovered, the ignition loss was 0.90% by mass and the dry weight was 1.9 kg (with the tertiary recovered product). do). The total weight of the primary recovered material, the secondary recovered material, and the tertiary recovered material was 10 kg, and almost all of the coal ash charged was recovered. When the primary recovered product and the tertiary recovered product were mixed, the weight was 8.2 kg, the ignition loss was calculated to be 0.59% by mass, and the ignition loss of the layer was deteriorated.

The composition and experimental conditions of the mixtures in Examples 4 to 6 and Comparative Example 3 are summarized in Table 3. In Comparative Example 3 in the table, the ignition loss of the primary recovered product is described as the residual amount of unburned carbon after the treatment (the same applies to Comparative Example 1 and Comparative Example 2 above).

1 Separation device 2 Separation tank 3 Water supply means 4 Micro bubble generator 5 Coal ash supply means 6 Side 7 Water supply port 8 Coal ash supply port 9 Discharge port 11 Water input device 12 Oil input device 13 Oil input device 14 Emulsification stirring device 15 Coal ash input device 16 Coal ash agitator 17 Slurry water input device 18 Slurry container 19 Water supply device 20 Micro bubble generator 21 Separation tank 22 Multi-layer filter press machine 23 Drying conveyor 24 Light layer filter press machine 25 Water / Oil separation tank 30 Separation device 31 Separation tank 32 Ball valve 41 Coal ash circulation path 42 Coal ash suction port 43 Coal ash discharge port 44 Coal ash circulation pump 51 Water circulation channel 52 Water suction port 53 Water discharge port 54 Water circulation pump 55 Micro bubble generator

Claims (10)

A separation tank that separates coal ash containing unburned carbon into unburned carbon and coal ash,
A water supply means for supplying new water into the separation tank from the water supply port provided at the bottom of the separation tank,
It is equipped with a bubble supply means that supplies bubbles into the separation tank from the bottom of the separation tank.
The separation tank is configured so that coal ash can be supplied from a position higher than the height of the water supply port .
The lower part of the separation tank constitutes a side that is narrowed downward,
A water supply port is provided on the above side,
A separation device provided so that the vicinity of the water supply port of the water supply means is substantially parallel to the tangential direction with respect to the circumference of the side portion. It is equipped with a coal ash supply means that supplies coal ash into the separation tank from a coal ash supply port provided at a position higher than the height of the water supply port.
A coal ash supply port is provided on the side of the separation tank,
The separation device according to claim 1, wherein the vicinity of the coal ash supply port of the coal ash supply means is provided so as to be substantially parallel to the tangential direction with respect to the circumference of the side portion of the separation tank. The separation device according to claim 1 or 2, wherein the bubble supply means is configured to supply bubbles from a water supply port. Equipped with a coal ash supply means that can supply coal ash from a position higher than the height of the water supply port,
The coal ash supply means supplies coal ash as a coal ash slurry containing coal ash and water, and finally to the total volume X (L) of the coal ash slurry and water to be charged into the separation tank. On the other hand, according to any one of claims 1 to 3, comprising means for adjusting the flow rate of the coal ash slurry supplied by the coal ash supply means to X × 9/100 to X × 55/100 (L / min). The separator described. A slurrying step of adding water to a first mixture containing coal ash containing unburned carbon, water, and oil to form a coal ash slurry.
A water supply process that supplies new water into the separation tank from the water supply port provided at the bottom of the separation tank,
The bubble supply process that supplies bubbles into the separation tank from the bottom of the separation tank,
The water supplying step and the bubble supplying step in the separation tank in a state where water and air bubbles of a predetermined amount is supplied, from a higher than the height of the water supply opening position, the coal ash slurry obtained by slurrying step, separation tank The coal ash supply process to be supplied inside and
Coal ash slurry supplied to the separation tank by the coal ash supply step, a layer containing water and coal ash, and separation step of separating into a light layer containing unburned carbon adsorbed oil
Have,
A method for producing coal ash, which produces coal ash with a reduced residual amount of unburned carbon. The first mixture contains 0.15-10% by weight of oil and has a solid content concentration of 65-90% by weight.
The method for producing coal ash according to claim 5, further comprising a stirring step of stirring the first mixture before the slurrying step. The method for producing coal ash according to claim 6, wherein the first mixture contains 5 to 30% by mass of water. The method for producing coal ash according to claim 6 or 7, wherein the first mixture contains 0.2 to 10% by mass of oil. The method for producing coal ash according to any one of claims 6 to 8, further comprising an emulsification step of pre-stirring and emulsifying the water and oil used in the first mixture before the stirring step. A coal ash cleaning system equipped with a coal ash agitator, a slurrying container, and a separation device.
The coal ash agitator
And coal ash containing unburned carbon, water and oil and stirring means for stirring the including second mixture
Equipped with
The slurry container is
Slurry forming means for forming a coal ash slurry by further adding water to the third mixture stirred by the stirring means.
Equipped with
The separator is
The coal ash slurry formed by the slurry forming means is put into a separation tank to which water and bubbles are supplied, and formed into a layer containing water and coal ash and a light layer containing unburned carbon adsorbed with oil. Separation means to separate
To prepare
Coal ash cleaning system.

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